2. Making a UART - USB pass through

It’s as simple as:

import pyb
import select

def pass_through(usb, uart):
   usb.setinterrupt(-1)
   while True:
      select.select([usb, uart], [], [])
      if usb.any():
         uart.write(usb.read(256))
      if uart.any():
         usb.write(uart.read(256))

pass_through(pyb.USB_VCP(), pyb.UART(1, 9600, timeout=0))